W-Ni-Fe 중합금의 미세조직 변화에 대한 μ-phase의 영향

김대건,김은표,김영도,Kim, Dae-Geon,Kim, Eun-Pyo,Kim, Yeong-Do 한국재료학회 2002 한국재료학회지 Vol.12 No.1

In this study, the 95W heavy alloys of 3/7, 5/5 and 7/3 of Ni/Fe ratio were sintered at the temperature range between 1420 and $1480^{\circ}C$ for 1h and their microstructures were discussed for an effect of the ${\mu}$-phase $(Fe_7W_6)$ on the microstructure. The ${\mu}$-phase was observed in the only 95W-1.5Ni-3.5Fe alloy of 3/7 and it is thought to be formed and grown from the surface of the W particle. The W particle was surrounded with the ${\mu}$-phase and there were only the W particles and this phase without Ni-Fe-W matrix at the most part. The ${\mu}$-phase changed the interphase structure in the alloy and the grain growth of the W was suppressed because of interrupting the solution-reprecipitation of the W. The W content in the matrix was considered to be lowered due to the interruption of the solution-reprecipitation and the formation of the ${\mu}$-phase in the .

솔-젤 법을 통해 제조된 강유전체 (Na,K)NbO₃ 막의 두께에 미치는 PVP의 영향

김대건,유인상,김세훈,김진호,Kim, Dae-Gun,Yoo, In-Sang,Kim, Sae-Hoon,Kim, Jin-Ho 한국재료학회 2012 한국재료학회지 Vol.22 No.12

(Na, K) $NbO_3$ thick film was successfully achieved using a sol-gel coating process with the addition of polyvinylpyrrolidone (PVP) to a metal alkoxide solution. The transparent coating solution, mixed with Nb:PVP = 1:1 in a molar ration, was synthesized by evaporating the solvent to over 62.5 wt%. Additive PVP increased the viscosity of the solution so that the coating thickness could be enhanced. The thickness of the (Na, K) $NbO_3$ film assisted by PVP was ca. 320 nm at the time of deposition; this value is four times thicker than that of the sample fabricated without PVP. Also, due to PVP binding with the OH groups of the metal alkoxide, the condensation reaction in the film was suppressed. The crystalline size of the (Na, K) $NbO_3$ films assisted by PVP was ca. 15 nm smaller than that of the film fabricated without PVP. After the sintering process at $700^{\circ}C$, the (Na, K) $NbO_3$ films were mainly composed of randomly oriented (Na, K) $NbO_3$ phase of perovskite crystal structure, including a somewhat secondary phase of $K_2Nb_4O_{11}$. However, by adding PVP, the content of the secondary phase became quite smaller than that of the sample without PVP. It was thought that the addition of PVP might have the effect of restraining the loss of potassium and that PVP could hold metalloxane by strong hydrogen bonding before complete decomposition. Therefore, the film thickness of the (Na, K) $NbO_3$ films could be considerably advanced and made more crack-free by the addition of PVP.

W-Cu 복합분말의 제조를 위한 기계화학적 공정에서 볼 밀링 시간에 따른 환원거동

김대건,이강원,석명진,김영도,Kim, Dae-Gun,Lee, Kang-Won,Suk, Myung-Jin,Kim, Young-Do 한국재료학회 2003 한국재료학회지 Vol.13 No.3

W-Cu composite powders can be prepared by mechanochemical process, where the $WO_3$-CuO composite powders were mechanically synthesized from the elemental oxide powders and subsequently reduced to W-Cu composite powders. In the present work, reduction behavior of$ WO_3$-CuO composite powders that were synthesized at different milling time was examined in terms of hygrometric analysis. In case of $WO_3$-CuO ball-milled for 20 h, the reaction temperature of CuO\longrightarrowCu became lower than in case of 1 h. Also, the reaction of $WO_3$\longrightarrow$WO_{2.9-2.72}$ and $WO_{2.9-2.72}$ \longrightarrow$WO_2$were shifted to lower temperatures and the peaks were changed to much sharper shape. While the reaction of $WO_2$\longrightarrowW in case of ball-milling for 20 h started at lower temperature, the peak temperature was the same as in 1 h ball-milling. The reduced W particle size was somewhat finer fer 20 h ball-milling. It was considered that the refinement of oxide particles caused by ball-milling process leads to such a change in the reduction behavior.

지열을 활용한 에너지 자원순환공법

김대건,Kim, Dae-Geon 한국건설순환자원학회 2016 한국건설순환자원학회지 Vol.11 No.1

IPTV 기술

김대건,Kim, Dae-Geon 한국통신학회 2007 정보와 통신 Vol.24 No.4

컨버전스시대의 꽃이라고 할 수 있는 IPTV 서비스는 세계 유수의 통신 사업자들을 중심으로 현재 빠르게 추진되고 있다. 이러한 IPTV 서비스의 세계적 추세에서 우리나라는 자타가 공인하는 세계 제일의 브로드밴드 강대국으로서, 이는 향후 다가올 컨버전스 시대에 강한 경쟁력 우위를 점할 수 있는 더할 수 없는 기회이다. 이에 본 기고에서는 IPTV에 관한 개요, 정책, 서비스, 요소기술, 국내외 현황 및 표준화에 대해 기술한다.

24개월 대기 노출된 Al1050 및 Al7075 알루미늄 합금 산화막에 대한 투과전자현미경 분석

김대건,김가림,최원준,반치범,Kim, Dae-Geon,Kim, Ga-Rim,Choi, Wonjun,Bahn, Chi Bum 한국표면공학회 2019 한국표면공학회지 Vol.52 No.2

Al1050 and Al7075 alloy specimens were exposed to atmospheric conditions for 24 months and analyzed by Transmission Electron Microscopy to characterize their corrosion behavior and oxide film characteristics, especially focusing on intergranular corrosion or oxidation. In general, the intergranular oxygen penetration depth of Al1050 was deeper than Al7075. Since O and Si signals were overlapped at the oxidized grain boundaries of Al1050 and Mg is not included in Al1050, it is concluded that Si segregated along the grain boundaries directly impacts on the intergranular corrosion of Al1050. Cr-Si or Mg-Si intermetallic particles were not observed along the grain boundaries of Al7050, but Mg-Si particle was barely observed in the matrix. 10-nm size Mg-Zn particles were also found all over the matrix. Mg was mainly observed along the oxidized grain boundary of Al7075, but Si was not detected due to the Mg-Si particle formation in the matrix and relatively low concentration of Si in Al7075. Therefore, it is thought that Mg plays an important role in the intergranular corrosion of Al7075 under atmospheric corrosion conditions.

WO₃-CuO의 수소환원거동에 미치는 볼 밀링의 영향

김대건,심우석,김영도,Kim, Dae-Gun,Shim, Woo-Seok,Kim, Young-Do 한국재료학회 2003 한국재료학회지 Vol.13 No.9

To fabricate W-Cu nanocomposite powder, $WO_3$-CuO powder mixture was high-energetically ball-milled and subsequently hydrogen-reduced. The effect of ball-milling on the hydrogen-reduction behavior of$ WO_3$-CuO was investigated with non-isothermal hygrometric analysis during hydrogen-reduction. Increasing the ball-milling time, the reduction peak temperatures of humidity curves were shifted to low temperature. It was considered that the reduction temperature should be decreased because the specific surface area of each oxide considerably increased with increasing the ball-milling time. In case of ball-milling for 0 h, $WO_3$and CuO were independently hydrogen-reduced and W particles were nucleated on the surface of Cu adjacent to W by CVT. However, in case of ball-milling for 50 h, the aggregates of about 200-300 nm were observed. W particles of size below 30-50 nm were homogeneously distributed with Cu in the aggregates.

통방 융합서비스(IPTV) 국내외 현황

김대건,Kim, Dae-Geon 한국통신학회 2007 정보와 통신 Vol.24 No.2

3단 의료정보 분석기법을 이용한 만성질환 관리 앰비언트 정보 시스템

김대건 ( Dae Gun Kim ),김문정 ( Mun Jung Kim ),김희재 ( Hee Jae Kim ),윤찬현 ( Chan Hyun Youn ) 한국정보처리학회 2010 한국정보처리학회 학술대회논문집 Vol.17 No.2

TMSM을 통한 검진 및 센싱 결과를 바탕으로 다량의 복잡한 의료 정보를 지능적으로 통합하는 의료 서비스 방식과 앰비언트 정보 시스템을 통한 시각화 시스템은 환자의 상태를 실시간으로 모니터링하며, 환자의 응급상황에 대하여 보다 유연하고 조기 적으로 대처할 수 있게 하여 정보 인지적 부담을 덜고, 인적, 진단 비용을 절약할 수 있다.

소득분위에 따른 중고령층의 사회참여 영향요인 연구

김대건(Kim Dae Gun) 호남대학교 인문사회과학연구소 2018 인문사회과학연구 Vol.60 No.1

본 연구는 중고령층의 소득에 따른 내부적 이질성에 기반하여 사회참여에 영향을 미치는 요인을 소득분위에 따라 확인한 연구이다. 중고령층 인구집단을 소득에 따라 4분위로 나누고 선행연구에 따라 제시된 사회참여 영향요인의 유효성을 확인하였다. 분석자료는 고령화연구패널 5차자료를 사용하였다. 분석에는 50세 이상 65세 미만의 2,791사례가 투입되었다. 분석결과 대부분의 사회참여 영향요인은 전체 중고령층집단에서 유의한 영향을 미치는 것이 확인되었다. 그러나 소득분위집단으로 구분하여 분석한 결과 소득이 높아짐에 따라 변수의 영향력은 순차적으로 상실되는 경향을 보이는 것으로 나타났다. 특히 가장 높은 소득수준을 보인 집단에서는 교육수준과 건강상태를 제외한 모든 변수가 설명력을 상실하는 것을 확인하였다. 본 연구는 분석결과에 기반하여 중고령층의 사회참여를 유도하는 다양한 정책들이 중고령층 개인의 소득수준 및 욕구에 따라 개별적으로 적용될 수 있는 정책적 탄력성을 가져야 함을 함의로 제시하였다. The purpose of this study is to investigate the factor which affects the civic engagement based on the internal heterogeneity according to the middle and old-aged people s income. This study was to divide the population group of middle and old-aged people according to the income in quartile and to confirm the effectiveness on the correlates of civic engagement suggested in preceding study. As for the analysis data, this study was to use Korean Longitudinal Study of Ageing(KLoSA). The result of this research is may be summed up as follows. This study has shown that the correlates of most of civic engagement had significant effect on the group of total middle and old-aged people. However, as a result of analyzing it by dividing it into the income distribution group, this study has found out that the influence of variables showed a tendency to be lost in consecutive order as income levels rose. In particular, at the group which showed the highest income level, the whole variable except the education level and health status lost its explanation power. Based on the analysis result, this study was to implicatively suggest that various policies which induced the civic engagement for the middle and old-aged people should have policy resilience which could be applied individually according to the individual income level and needs for the middle and old-aged people.